I got tired of stopping every time I wanted some water from my nalgene bottle. I love my nalgene, don't get me wrong, but it's impossible to drink water while riding. This water bottle not only keeps my water nice and cold, it's easy to drink while riding, although I wouldn't recommend it for mountain biking since dust can easily get around the mouth piece and you'll end up squirting some dirt into your mouth along with water. Overall, I use it for road biking and spinning and this water bottle works well.
UPDATE: I've dropped a star cause I can't seem to get rid of the silicon taste that the bottle leaches into my water. I thought it'd go away after a couple uses but nothing is getting rid of the nasty chemical taste. I'd return the bottle but it's not worth the hassle.